The detection and avoidance of power lines, guy wires, and other small curvilinear obstacles while flying an aircraft is of critical importance in ensuring flight crew safety and continued flight operations. With military aircraft especially, low altitude flights (e.g., below 1,000 ft.) are common in support of a variety of missions. Generally, military aircraft comprise fixed wing and rotary wing, in addition to manned and unmanned configurations. Similarly, commercial aircraft such as news helicopters and small private aircraft also fly at low altitudes and must also have an awareness of small obstacles such as power lines. The power lines, however, are difficult to identify due to their small size and aspect. With increasing pilot workload in the cockpit relative to other flight systems, detection of power lines becomes an even more difficult task.
Obstacle detection can further be categorized into active and passive detection. Active detection involves transmission of a signal from the aircraft to the obstacle and subsequent reception of a signal by the aircraft back from the obstacle, e.g. radar. Passive detection involves only reception of a signal from the obstacle by the aircraft such that the aircraft is not transmitting any signals, e.g. infrared imaging. Active detection becomes undesirable in instances where the aircraft must remain covert and undetectable, as required in many military missions. Further, the transmissions from active detection systems may interfere with other flight instruments and cause problems with flight operations. Passive detection of obstacles, therefore, is highly desirable in many applications.
Due to stringent performance requirements of many aircraft, related hardware for obstacle detection systems must be as compact and lightweight as possible. However, because power lines are inherently small, high resolution equipment is required to detect an obstacle of such small size. Unfortunately, higher resolution equipment is larger and heavier, and further more costly. As a result, high resolution systems for power line detection can be performance and cost inhibiting on certain aircraft platforms.
Typically, small obstacles such as power lines are identified simply with the eyesight of the pilot, and in some instances, image software and hardware on-board the aircraft. One obstacle detection system of the known art is the Digital Terrain Elevation Database (DTED), which is a system having a database of obstacles with their respective spatial coordinates. Accordingly, the DTED system alerts the pilot to known obstacles in the database during flight operations. Unfortunately, only a limited number of obstacles are loaded in the database, and therefore, the pilot must remain alert to obstacles not previously loaded therein. In addition to an incomplete database, such a system can further provide a false sense of security to the flight crew, resulting in increased safety risks.
Additional known art obstacle detection systems include Millimeter Wave Radar (MMW Radar) and Laser Radar (LADAR). However, the radar systems are active and thus are undesirable during covert flight operations since the radar transmissions can be detected, and further due to potential interference between the radar transmissions and other flight instruments. Additionally, some radar systems are incapable of real-time processing, such that a longer period of time is required between obstacle detection and initiating an evasive maneuver to avoid the obstacle. Moreover, the radar systems are generally expensive, large, and heavy, and as a result may be prohibitive on certain aircraft platforms.
Yet a further detection system of the known art measures the electromagnetic radiation emanating from power lines to detect the presence of the lines during flight operations. Electromagnetic radiation detection, however, is subject to the variations in electricity demands in areas of modest population density. As a result, the ranges of electromagnetic radiation that trigger an alarm vary greatly, and thus, the detection systems are unpredictable in areas of high electromagnetic variations. Moreover, many electromagnetic radiation systems are incapable of real-time processing, which increases the minimum distance between the aircraft and the obstacle for reliable warnings.
Accordingly, there remains a need in the art for a real-time, passive obstacle detection system that is lightweight, compact, and affordable. The detection system must further be applicable to a variety of aircraft platforms and easily retrofittable with existing aircraft systems.